Cite this: CrystEngComm, 2013, 15, 1563 Control over the preparation of two pH-dependent Cu(II) supramolecular isomers based on 1,3,5- benzenetricarboxylic acid and the bis(4- pyridylthio)methane ligand3 Received 10th October 2012, Accepted 30th November 2012 DOI: 10.1039/c2ce26652k www.rsc.org/crystengcomm Ana Bele ´n Lago,* Rosa Carballo, Sabina Rodrı ´guez-Hermida and Ezequiel M. Va ´zquez-Lo ´pez The possibility of controlling the formation of copper(II) coordination polymers based on the rigid carboxylate ligand 1,3,5-benzenetricarboxylic acid (H 3 btc) and an N,N-divergent spacer with conforma- tional flexibility, bis(4-pyridylthio)methane (SCS), was investigated. The new coordination polymers 1 ‘ [Cu(H 2 btc) 2 (SCS)] (1) and 2 ‘ [Cu(Hbtc)(SCS) 2 ]?H 2 O(2) have been prepared and characterized. Compounds 1 and 2 were obtained as a mixture and optimization of the synthetic conditions allowed the isolation of pure phases in high yield. Topological analysis showed the interpenetration of three networks with a vcm- type topology in 2. The thermal stability and the structural dynamics of these systems have also been investigated. Introduction The use of metal–ligand interactions in the construction of polymers has received increasing attention in the fields of supramolecular chemistry and crystal engineering in recent years. 1 Nevertheless, the control and prediction of the structures of this kind of material continue to be amongst the main challenges in the preparation of such compounds. 2 Many of the architectures reported to date are based on rigid linear linker ligands, with less effort focused on the use of ligands with conformational flexibility 3 or the use of combina- tions of rigid and flexible ligands. One of the most effective approaches for the rational and controllable preparation of polymers may involve the appro- priate choice of organic bridging ligands. 4 In this sense, the flexible twisted molecule bis(4-pyridylthio)methane (SCS, Scheme 1) has proven to be a suitable N,N-divergent ligand that allows polymerization through coordination bonds. 5 As far as rigid ligands are concerned, 1,3,5-benzenetricar- boxylic acid (H 3 btc, Scheme 1) is a planar molecule that contains three carboxylic acid groups. These groups can lead to several possible coordination modes that can be modulated by control of the pH of the media. These characteristics have made H 3 btc one of the most extensively used ligands in the synthesis of multidimensional compounds. 6 Supramolecular isomerism, i.e. the ability of a substance to exist in more than one type of network superstructure with the same molecular building blocks, is of importance because the superstructure plays a key role in the properties of crystalline materials. 7 It is well known, however, that numerous factors can influence the structures and topologies of coordination polymers. 8 The preparation of supramolecular isomers is very sensitive to the synthetic conditions and this makes it extremely difficult for synthetic chemists due to the low formation energy differences between isomers. 9 Meticulous control of all the synthetic factors is required to obtain a Departamento de Quı ´mica Inorga ´nica, Facultade de Quı ´mica, Universidade de Vigo, E-36310 Vigo, Galicia, Spain. E-mail: ablago@uvigo.es; Fax: +34-986812556; Tel: +34-986812273 3 Electronic supplementary information (ESI) available: IR and UV-vis. spectra, X-ray power diffratograms and thermal stability studies (TGA, DSC and X-ray power diffractograms). CCDC 905301 and 905302. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c2ce26652k Scheme 1 CrystEngComm PAPER This journal is ß The Royal Society of Chemistry 2013 CrystEngComm, 2013, 15, 1563–1570 | 1563 Downloaded by Universidad de Vigo on 30 January 2013 Published on 03 December 2012 on http://pubs.rsc.org | doi:10.1039/C2CE26652K View Article Online View Journal | View Issue